package com.wc.blue_bridge_test.base.T3;

import java.math.BigDecimal;
import java.util.Scanner;

/**
 * @Author congege
 * @Description
 * @Date Created in 2023/12/24-12:31
 */
public class Main {
    public static void main(String[] args) {
        double pi = 3.14159265358979323;
        Scanner sc = new Scanner(System.in);
        int r = sc.nextInt();
        BigDecimal num1 = new BigDecimal(r * r * pi);
        num1 = num1.setScale(7,BigDecimal.ROUND_HALF_UP);
        System.out.println(num1);
    }
    static double round(double val, int radix) {
        double dit = Math.pow(10, radix);
        return Math.round(val * dit) / dit;
    }
}
